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Search Results: 1 - 10 of 2896 matches for " Yoshiyuki Kato "
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Efficient Protein Refolding Using Surfactants at High Final Protein Concentration  [PDF]
Hidetaka Noritomi, Yoshiyuki Kato, Satoru Kato
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.41002
Abstract:

The refolding of denatured hen egg white lysozyme (HEWL) was examined by surfactants at a high final refolded HEWL concentration (1 mg/mL). Hexadecyltrimethylammonium bromide (CTAB) and sucrose fatty acid monoester (DK-SS) were used to dissolve denatured HEWL without denaturants such as guanidine hydrochloride (GuHCl) and urea. When denatured HEWL was perfectly dissolved in buffer solutions containing surfactants and dithiothreitol (DTT), the concentration of CTAB was about one-twentieth times less than that of DK-SS. The concentration of CTAB strongly affected the refolding yield, and the maximum refolding yield was obtained at 0.88 mM CTAB, which is around the critical micelle concentration of CTAB. The refolding yield was influenced by the molar ratio of oxidized glutathione (GSSG) to DTT, and the maximum refolding yield was obtained when [GSSG]/[DTT] was 1.5. The refolding yield was markedly dependent upon the solution pH of HEWL, and exhibited 80% at pH 5.2.

Contrast Enhancement of Posterior Mediastinal Ganglioneuromas—Correlation between the Level of Enhancement and Histopathological Features  [PDF]
Yoshiyuki Ozawa, Masaki Hara, Maho Kato, Shigeki Shimizu, Yuta Shibamoto
Open Journal of Radiology (OJRad) , 2014, DOI: 10.4236/ojrad.2014.41016
Abstract:

Purpose: Relationship between CT or MR images and histological findings, especially vascularity, has not been adequately evaluated. The purpose of this study was to investigate correlation between contrast enhancement on CT and MRI and histological findings in posterior mediastinal ganglioneuromas. Materials and Methods: Contrast-enhanced (CE) CT (n = 11) and CE MRI (n = 5) of 12 patients with ganglioneuroma were reviewed. The attenuation, signal intensity, and dynamic enhancement pattern of the tumors were evaluated. The vascularity was histologically evaluated by the numbers of vessels. Results: Enhancement on CE-CT was none, mild, moderate, and high enhancement in 5 (45%), 2 (18%), 3 (27%), and 1 (9%) of the 11 lesions, respectively. Dynamic MRI showed mild, moderate and high enhancement in 3 (60%), 1 (20%) and 1 (20%) cases, respectively. The level of contrast enhancement correlated well only with the number of capillary vessels (r = 0.79, P = 0.0037). Conclusion: The posterior mediastinal ganglioneuromas sometimes show insufficient enhancement particularly on CE-CT. The level of enhancement might correlate with the amount of capillary vessels.

HV Virginis and WZ Sge-Type Dwarf Novae
Taichi Kato,Yoshiyuki Sekine,Ryuko Hirata
Physics , 2001, DOI: 10.1093/pasj/53.6.1191
Abstract: A dwarf nova HV Vir was observed photometrically for eight nights during the outburst in 1992 April - May. The star showed two distinct types of periodic variation: (1) 82.20-min (0.05708 d) double-humped variation with decaying amplitudes during the early stage of the outburst, and (2) 83.80-min (0.05820 d) superhumps in later stages. We attributed the former to "early superhumps", which are only seen in the earliest stage of WZ Sge-type outbursts. The superhump period and evolution of the superhumps, together with general characteristics of the light curve, make HV Vir a typical WZ Sge-type dwarf nova. HV Vir also showed a large increase of the superhump period during the superoutburst. Upon the recognition of the WZ Sge-type nature of an object previously considered as a nova, we present a comprehensive list of candidates for WZ Sge-type dwarf novae, and related systems.
Control of Genetically Prescribed Protein Tyrosine Kinase Activities by Environment-Linked Redox Reactions
Izumi Nakashima,Yoshiyuki Kawamoto,Kozue Takeda,Masashi Kato
Enzyme Research , 2011, DOI: 10.4061/2011/896567
Abstract: Recent observations on environment-linked control of genetically prescribed signaling systems for either cell activation or cell death have been reviewed with a focus on the regulation of activities of protein tyrosine kinases (PTKs). The environment-linked redox reactions seem to primarily affect cell surface receptors and cell membrane lipid rafts, and they induce generation of reactive oxygen species (ROS) in cells. ROS thus generated might upregulate the catalytic activities of PTKs through inactivating protein tyrosine phosphatases that dephosphorylate and inactivate autophosphorylated PTKs. Recent evidence has, however, demonstrated that ROS could also directly oxidize SH groups of genetically conserved specific cysteines on PTKs, sometimes producing disulfide-bonded dimers of PTK proteins, either for upregulation or downregulation of their catalytic activities. The basic role of the redox reaction/covalent bond-mediated modification of protein tertiary structure-linked noncovalent bond-oriented signaling systems in living organisms is discussed. 1. Introduction Enzymes, of which structures and functions are prescribed in genes, basically mediate all metabolisms needed for the development and functions of living organisms. Among the many enzymes, protein tyrosine kinases (PTKs) are known to play key roles in intracellular signaling for the development and functions of cells [1]. The mechanisms for regulation of the catalytic activities of PTKs seem to be principally prescribed in genes. These mechanisms include phosphorylation and dephosphorylation of specific tyrosine residues on the kinase protein by other PTKs or protein tyrosine phosphatases (PTPs), the structures and functions of which are all under genetic control [2–8]. For example, the catalytic activity of Src, a representative PTK, is known to be downregulated through phosphorylation of Tyr527 located in the tail of Src protein by CSK, another PTK, which leads to binding of the tail to the specific structure on the SH2 domain of Src to make the catalytic domain of Src closed [2, 3]. Additionally, it is known to be upregulated by dephosphorylation of phosphorylated Tyr527, which allows the catalytic domain to open, inducing phosphorylation of Tyr416 as the major autophosphorylation site and upregulation of the kinetic activity to phosphorylate exogenous specific substrates [2–4, 7, 8]. On the other hand, dephosphorylation of phosphorylated Tyr416 by PTPs downregulates the kinase activity [5, 6, 8]. Results of several early studies have, however, suggested that the catalytic activities of
Curvature Entropy for Curved Profile Generation
Yoshiki Ujiie,Takeo Kato,Koichiro Sato,Yoshiyuki Matsuoka
Entropy , 2012, DOI: 10.3390/e14030533
Abstract: In a curved surface design, the overall shape features that emerge from combinations of shape elements are important. However, controlling the features of the overall shape in curved profiles is difficult using conventional microscopic shape information such as dimension. Herein two types of macroscopic shape information, curvature entropy and quadrature curvature entropy, quantitatively represent the features of the overall shape. The curvature entropy is calculated by the curvature distribution, and represents the complexity of a shape (one of the overall shape features). The quadrature curvature entropy is an improvement of the curvature entropy by introducing a Markov process to evaluate the continuity of a curvature and to approximate human cognition of the shape. Additionally, a shape generation method using a genetic algorithm as a calculator and the entropy as a shape generation index is presented. Finally, the applicability of the proposed method is demonstrated using the side view of an automobile as a design example.
Rac1-Dependent Lamellipodial Motility in Prostate Cancer PC-3 Cells Revealed by Optogenetic Control of Rac1 Activity
Takuma Kato, Katsuhisa Kawai, Youhei Egami, Yoshiyuki Kakehi, Nobukazu Araki
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0097749
Abstract: The lamellipodium, an essential structure for cell migration, plays an important role in the invasion and metastasis of cancer cells. Although Rac1 recognized as a key player in the formation of lamellipodia, the molecular mechanisms underlying lamellipodial motility are not fully understood. Optogenetic technology enabled us to spatiotemporally control the activity of photoactivatable Rac1 (PA-Rac1) in living cells. Using this system, we revealed the role of phosphatidylinositol 3-kinase (PI3K) in Rac1-dependent lamellipodial motility in PC-3 prostate cancer cells. Through local blue laser irradiation of PA-Rac1-expressing cells, lamellipodial motility was reversibly induced. First, outward extension of a lamellipodium parallel to the substratum was observed. The extended lamellipodium then showed ruffling activity at the periphery. Notably, PI(3,4,5)P3 and WAVE2 were localized in the extending lamellipodium in a PI3K-dependent manner. We confirmed that the inhibition of PI3K activity greatly suppressed lamellipodial extension, while the ruffling activity was less affected. These results suggest that Rac1-induced lamellipodial motility consists of two distinct activities, PI3K-dependent outward extension and PI3K-independent ruffling.
Magnetoencephalography Study of Right Parietal Lobe Dysfunction of the Evoked Mirror Neuron System in Antipsychotic-Free Schizophrenia
Yutaka Kato, Taro Muramatsu, Motoichiro Kato, Yoshiyuki Shibukawa, Masuro Shintani, Masaru Mimura
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0028087
Abstract: Introduction Patients with schizophrenia commonly exhibit deficits of non-verbal communication in social contexts, which may be related to cognitive dysfunction that impairs recognition of biological motion. Although perception of biological motion is known to be mediated by the mirror neuron system, there have been few empirical studies of this system in patients with schizophrenia. Methods Using magnetoencephalography, we examined whether antipsychotic-free schizophrenia patients displayed mirror neuron system dysfunction during observation of biological motion (jaw movement of another individual). Results Compared with normal controls, the patients with schizophrenia had fewer components of both the waveform and equivalent current dipole, suggesting aberrant brain activity resulting from dysfunction of the right inferior parietal cortex. They also lacked the changes of alpha band and gamma band oscillation seen in normal controls, and had weaker phase-locking factors and gamma-synchronization predominantly in right parietal cortex. Conclusions Our findings demonstrate that untreated patients with schizophrenia exhibit aberrant mirror neuron system function based on the right inferior parietal cortex, which is characterized by dysfunction of gamma-synchronization in the right parietal lobe during observation of biological motion.
Delivery of Plasmid DNA into Tumors by Intravenous Injection of PEGylated Cationic Lipoplexes into Tumor-Bearing Mice  [PDF]
Yoshiyuki Hattori
Pharmacology & Pharmacy (PP) , 2016, DOI: 10.4236/pp.2016.77034
Abstract: For systemic injection of cationic liposome/plasmid DNA (pDNA) complexes (cationic lipoplexes), polyethylene glycol (PEG)-modification (PEGylation) of lipoplexes can enhance their systemic stability. In this study, we examined whether intravenous injection of PEGylated cationic lipoplexes into tumor-bearing mice could deliver pDNA into tumor tissues and induce transgene expression. PEGylation of cationic liposomes could prevent their agglutination with erythrocytes. However, when PEGylated cationic lipoplexes were injected intravenously into tumor-bearing mice, they accumulated in tumor vascular vessels and did not exhibit transgene expression in tumors with both poor and well-developed vascularization. Furthermore, PEGylated cationic lipoplexes of CpG- free pDNA could not increase transgene expression in tumors after intravenous injection. These results suggested that PEGylation could not extravasate cationic lipoplexes from vascular vessels in tumors and abolished transgene expression although it enhanced the systemic stability of cationic lipoplexes by avoiding interactions with blood components such as erythrocytes. Successful delivery of pDNA to tumors by PEGylated cationic liposomes will require a rational strategy and the design of liposomal delivery systems to overcome the issue associated with the use of PEG.
Atomistic mechanism of perfect alignment of nitrogen-vacancy centers in diamond
Takehide Miyazaki,Yoshiyuki Miyamoto,Toshiharu Makino,Hiromitsu Kato,Satoshi Yamasaki,Takahiro Fukui,Yuki Doi,Norio Tokuda,Mutsuko Hatano,Norikazu Mizuochi
Physics , 2014, DOI: 10.1063/1.4904988
Abstract: Nitrogen-vacancy (NV) centers in diamond have attracted a great deal of attention because of their possible use in information processing and electromagnetic sensing technologies. We examined theatomistic generation mechanism for the NV defect aligned in the [111] direction of C(111) substrates. We found that N is incorporated in the C bilayers during the lateral growth arising from a sequence of kink propagation along the step edge down to [-1,-1,2]. As a result, the atomic configuration with the N-atom lone-pair pointing in the [111] direction is formed, which causes preferential alignment of NVs. Our model is consistent with recent experimental data for perfect NV alignment in C(111) substrates.
Suppression of Methane Gas Emissions and Analysis of the Electrode Microbial Community in a Sediment-Based Bio-Electrochemical System  [PDF]
Yoshiyuki Ueno, Yoji Kitajima
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.45032
Abstract:

The effects of bioelectrochemical systems (BESs) for the suppression of methane gas emissions from sediment were examined using a laboratory-scale reactor system. Methane gas emissions from acetate were suppressed by approximately 36% from control based on the installation of a BES in which carbon-graphite electrodes were buried in sediment and arbitrarily set at certain oxidative potentials (+300 mV vs Ag/AgCl) using a potentiostat. Meanwhile, methane gas emissions increased in the BES reactor where the electrode potential was set at -200 mV. Results obtained from pyrotag sequencing analysis of the microbial community on the surface of the buried electrodes targeting 16S rRNA genes demonstrated that the genusGeobacterhad drastically propagated in a sample from the reactor where the electrodes were buried. Quantitative analysis of 16S rRNA genes of archaea also revealed that the archaeal population had decreased to approximately 1/6 of its original level on the electrode of the BES set at +300 mV. This implied that the oxidation-reduction potential (ORP) in the sediment was raised to the inhibition level for methanogenesis in the vicinity of the buried electrode. Analysis of electron flux in the experiment revealed that electrons intrinsically used for methanogenesis were recovered via current generation in the sediment where a potential of +300 mV was set for the electrode, although most electrons donated from acetate were captured by oxygen respiration and other electron-accepting reactions. These results imply that BES technology is suitable for use as a tool for controlling re-dox-dependent reactions in natural environments, and that it also brought about changes in the microbial population structure and methanogenic activity in sediment.

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